CERN scientists create antihydrogen atoms

SummaryPrimordial antimatter has so far never been observed in the universe, and its absence remains a scientific enigma.

CERN physicists have succeeded for the first time in producing a beam of antihydrogen atoms, an advance that brings scientists closer to solving the antimatter mystery.

Physicists from CERN's Atomic Spectroscopy and Collisions Using Slow Antiprotons (ASACUSA) experiment said they have produced at least 80 atoms of antihydrogen.

Primordial antimatter has so far never been observed in the universe, and its absence remains a scientific enigma.

Nevertheless, it is possible to produce significant amounts of antihydrogen in experiments at the Geneva-based European Organisation for Nuclear Research (CERN) by mixing antielectrons (positrons) and low energy antiprotons produced by the Antiproton Decelerator.

The spectra of hydrogen and antihydrogen are predicted to be identical, so any tiny difference between them would immediately open a window to new physics, and could help in solving the antimatter mystery.

It has been a puzzle to scientists why humans, stars and the universe are made of matter, rather than of antimatter.

With its single proton accompanied by just one electron, hydrogen is the simplest existing atom, and one of the most precisely investigated and best understood systems in physics.

Thus comparisons of hydrogen and antihydrogen atoms constitute one of the best ways to perform highly precise tests of matter/antimatter symmetry, researchers said.

Matter and antimatter annihilate immediately when they meet, so aside from creating antihydrogen, one of the key challenges for physicists is to keep antiatoms away from ordinary matter.

To do so, experiments take advantage of antihydrogen's magnetic properties (which are similar to hydrogen's) and use very strong non-uniform magnetic fields to trap antiatoms long enough to study them.

However, the strong magnetic field gradients degrade the spectroscopic properties of the (anti)atoms.

To allow for clean high-resolution spectroscopy, the ASACUSA collaboration developed an innovative set-up to transfer antihydrogen atoms to a region where they can be studied in flight, far from the strong magnetic field.

"Antihydrogen atoms having no charge, it was a big

challenge to transport them from their trap," said Yasunori Yamazaki of RIKEN, Japan, a team leader of the ASACUSAcollaboration.

"Our results are very promising for high-precision studies of antihydrogen atoms, particularly the hyperfine structure, one of the two best known spectroscopic properties of hydrogen.

"Its measurement in antihydrogen will allow the most sensitive test of matter/antimatter symmetry. We are looking forward to restarting this summer with an even more improved set-up," Yamazaki said in a statement.